and environmental toxicity, and affect the esthetic quality of the water environment. Removal of heavy metal ions from water resources is important from an environmental protection point of view, because they cause pollution of natural waters and subsequent metal accumulation in the food chain. Hexavalent chromium exists in water as oxyanions such as chromate, HCrO 4 − , and dichromate, the speciation being dependent on pH. Such ions are toxic, carcinogenic, mutagenic, and teratogenic [1,2]. The toxicity of vanadium is also well known [3]. Molybdenum has long been known as one of the biologically active transition elements. Subchronic and chronic oral exposures can result in gastrointestinal disturbances, growth retardation, anemia, hypothyroidism, bone and joint deformities, sterility, liver and kidney abnormalities, and death. Tungsten is an important strategic metal that is used in a variety of industrial applications. Tungsten is released to the environment, e.g., through its use in winter tires. The biogeochemical behavior of W is poorly known. However, it is known that the WO 4 2− ion has an antagonistic effect on the metabolism of MoO 4 2− [4]. Therefore, removal of these ions from water and also determination of their trace amounts in water samples is of great importance. Study for the introduction of efficient methods for the removal and preconcentration of the heavy metal ions, including the above mentioned ions, is interesting to the researchers yet.Different methods have been developed to preconcentration and removal of metal ions from water samples. These include precipitation, ion exchange, membrane separation and adsorption. Among these methods, solid phase extraction has been shown to be an economical alternative for removing trace metals from water [5][6][7][8][9]. In solid phase extraction a suitable sorbent is used as extracting phase and removal or preconcentration takes place by physisorption and/or chemisorption. Abstract Ni 0.5 Zn 0 . 5 Fe 2 O 4 nanocomposite was synthesized and used for the removal and preconcentration of Cr(VI), Mo(VI), V(V) and W(VI) ions. The effect of various parameters such as pH, amount of the adsorbent and contact time on the adsorption efficiency of Cr(VI), Mo(VI), V(V) and W(VI) ions on the adsorbent were studied. The maximum adsorption occurred at pH 4.0 for Cr(VI) and W(VI) and at pH 5.0 for Mo(VI) and V(V). Maximum adsorption capacity (q max ) was estimated using Langmuir adsorption model as 48.5, 38.8, 28.0 and 72.0 mg g −1 for Cr(VI), Mo(VI), V(V) and W(VI) ions, respectively. The adsorbed oxyanions were then desorbed by NaOH solution. The concentration of the ions in desorbed solution was determined spectrophotometrically. Calibration curves were linear for Cr(VI), Mo(VI), V(V) and W(VI) ions in the range 0.7-150.0, 0.9-70.0, 2.0-50.0 and 1.0-40.0 ng mL −1 for an initial sample solution of 100 mL, respectively.Keywords Magnetic nanocomposite · Nickel-zinc ferrite · Cr(VI), Mo(VI), V(V) and W(VI) oxyanions · Water purification · Preconcentration

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Using cloud computing, businesses can adopt IT without incurring a significant upfront cost. The Internet has numerous benefits, but model security remains a concern, which affects cloud embracing negatively. The security challenge gets too difficult underneath data center, while additional dimensions such as model design, multitenancy, elasticity, and the layers dependency stack have been added to the problem scope. We present a thorough examination of the cloud security challenge in this article. We looked at the issue from the standpoints of network infrastructure: cloud-provided features, cloud consumers, and cloud service delivery methods. Based on this research, we developed an in-depth characterization of the data protection challenge and recommended security solutions that should address the critical aspects of the issue. Cloud computing is an exploding field of research that relies on distributing computing power instead of using dedicated computers or smart devices. Most of the growth in this sector is attributed to the indispensability of electronic and digital gadgets and the shift from a traditional IT subscription model to a unique cloud model. Cloud computing offered a significant danger and difficulty for information system projects, but it also provided them with several possibilities to improve their data processing. It has also been noted that cloud users and consumers do not yet have the necessary forensic skills to detect illegal activity in the cloud. Although the cloud offers potential technological and economic advantages, consumers have been reluctant to adopt it primarily due to security concerns and the difficulty of conducting an appropriate investigation into the cloud. Some study has been done in this area, and strategies for conducting forensic investigations have been proposed. In this research paper, we begin by analyzing the intrusion detection progress made by other academics, and then we analyze and evaluate our conclusions in order to assess the potential difficulties that cloud forensics face based on these findings.

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